Breast cancer cells switch to ‘survival mode' to escape death

New research has revealed how breast cancer cells avoid being killed by antiestrogen drugs, such as tamoxifen.

Dr Patricia V Schoenlein and colleagues at the Medical College of Georgia found that breast cancer cells that possess estrogen receptors have the ability to reorganize themselves and switch to a survival mode called macroautophagy – a strategy also used by normal cells when faced with starvation – in the presence of antiestrogen drugs. The researchers found that breast cancer cells took just one week to reorganize their cellular components and switch to macroautophagy, a state in which they cannot grow or replicate. The cells were found to remain in survival mode until antiestrogen treatment ended, or until they mutated and became resistant to the drugs, then they would switch back to normal mode and begin growing and dividing again.

Laboratory tests showed that just 20-25% of cancer cells were killed when continuously exposed to antiestrogen drugs. Thus, meaning that approximately 75% of cells survive the treatment, however adding a macroautophagy inhibitor to the treatment “promoted robust cell death.”

"We believe targeting the autophagosome function will significantly improve the efficacy of hormonal treatment for estrogen-positive breast cancer," said Dr Schoenlein in a news release issued by the Medical College of Georgia. The researchers believe that the malaria drug chloroquine may be able to block macroautophagy, and they hope to test its effectiveness in combination with antiestrogen drugs.

News release: Breast cancer cells recycle to escape death by hormonal therapy. Medical College of Georgia Website. October 2nd 2008.